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Yellow Cannabis Leaves

It’s better to read this marijuana blog and not need it than to not read it and come undone in the grow room. Sometimes things go wrong in the cannabis garden. Even the best marijuana growers can run into trouble occasionally and yellow leaves are usually the first warning sign.

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7 Jun 2017

No grower wants to see yellow leaves. Withering plants in the grow op are a miserable sight. Unfortunately not every cannabis crop grows trouble free. This can be due to incalculable reasons. It can be anything from grower errors to invasive microorganisms. Of course, we cannot provide you with a surefire silver bullet solution for every potential cannabis plant malady. We’re cannabis writers, not clairvoyants.

But we certainly can help you. Specifically to correctly identify most of the common causes for yellow leaves. Moreover, we have included helpful tips to treat ailing plants. Plus simple pro tips and tricks. Any home grower can implement our advice to avoid cannabis plants' leaves turning yellow. Now let’s get into the specifics.

ACCURATE DIAGNOSIS

The very first step is accurate diagnosis. What is the cause of the yellow leaves spoiling your cannabis plants? Chlorosis in ordinary decent grower terms means loss of chlorophyll. In order to effectively apply treatment, you must know what you’re dealing with. Don’t jump to conclusions. Don’t panic. The leaves on your cannabis plants are like biological solar panels. They are essential to photosynthesis. Removing all the yellow leaves is not recommended surgery, especially for young plants. Correct identification of the source of the problem and swift remedial action can restore marijuana.

Senescence is when plants will naturally yellow off and die. During the final weeks of flowering do not be alarmed. Leaf drop and yellowing always increases. Flushing plants with pure water or a flushing solution at the end of bloom will also rid the medium of residual nutrients and often causes leaves to yellow.

COMMON CAUSES OF YELLOW LEAVES

The following is not a definitive list of the causes for chlorosis. It is such a common symptom, that sick plants display, we could write a book, but not today. That being said, we have focused on the most common causes for yellow leaves based on first hand pro grower experiences. If you are presently troubleshooting for a solution to chlorosis, read the next few sections carefully. Your crop could be riding on it.

THE MOST COMMON GROWER ERRORS

UNDER/OVERWATERING

Cannabis plants will only thrive with an effective wet-dry cycle. This means you must water the right amount at the right time, with every watering. So what's the best way to tell if your marijuana is thirsty? Lift up the containers when they are dry. Then again after watering, so you will know the difference.

Perhaps it’s not possible to easily lift plants? Then you can purchase a humidity meter to insert into the pot. Hydro growers need to ensure pumps, air stones, reservoirs and timers are set up correctly from the start of the grow. Check twice, and then check again.

Treatment: Monitor the plant's post feeding behaviour closely. Use one of the measures above to more accurately gauge when to water to prevent recurrence. Too much water can lead to root rot. Too little water will stunt growth. Keep a grow diary if you must and try to get into a routine as the grow progresses.

Treatment: Monitor the plant's post feeding behaviour closely. Use one of the measures above to more accurately gauge when to water to prevent recurrence. Too much water can lead to root rot. Too little water will stunt growth. Keep a grow diary if you must and try to get into a routine as the grow progresses.

PH AND NUTRIENT LOCKOUT

Soil growers have the advantage of cultivating in a medium, that acts as a buffer for roots. Hydroponics and coco are not quite as forgiving to pH imbalances. Even soil growers need to at least come close to getting the ideal pH of 6.0-7.0 and maintain it, otherwise plants will suffer. 5.5 to 6.5 pH is generally agreed upon as the recommended range for hydro and coco. Yellow leaves can be a warning sign, that you don’t have your nutes dialled in and the pH is off.

Essentially when the pH of your nutrient solution strays above or below the particular sweet spot for your substrate, it prevents complete absorption of all the elements of the solution. Roots are starved of certain nutrients and micronutrients as the incorrect pH causes a lockout.

Treatment: Invest in a pH pen or cannabis fertilisers with pH-perfect solutions, that can auto adjust a wider pH range. Flush plants with pure water and then resume feeding with a light dialled in solution to suit your growing medium. Also, make sure that the base nutrients you use contain all of the essential microelements or you will have to add extra bottles of supplements to the budget.

Treatment: Invest in a pH pen or cannabis fertilisers with pH-perfect solutions, that can auto adjust a wider pH range. Flush plants with pure water and then resume feeding with a light dialled in solution to suit your growing medium. Also, make sure that the base nutrients you use contain all of the essential microelements or you will have to add extra bottles of supplements to the budget.

OVER/UNDERFERTILISATION

Again, plants need just the right nutrients at the right time. Read the dosage instructions on the label of every bottle of fertiliser before adding to water. Furthermore, we highly recommend you consult the website of the brand of nutrients you are using as most feature custom charts and feeding schedules.

Treatment: As you might have guessed, begin treatment with a flush of pure water. Then follow up with the manufacturers recommended dose at the particular growth/flowering stage. A good rule of thumb is to increase doses incrementally and monitor plant behaviour before further increasing the strength of the solution.

Treatment: As you might have guessed, begin treatment with a flush of pure water. Then follow up with the manufacturers recommended dose at the particular growth/flowering stage. A good rule of thumb is to increase doses incrementally and monitor plant behaviour before further increasing the strength of the solution.

LIGHT BURNS AND DEFICIENCIES

Indoor cannabis plants grown under artificial lights must be perfectly positioned and lamps must be in just the right distance above the canopy for best results. When lamps and reflectors are too close to the flowering tops, buds and leaves will be yellow and brown as the light is too intense. This is very much a top down problem.

In contrast, too little light is usually a problem, that is most evident from the bottom up. Light deficiency causes shaded leaves or leaves too far below the light penetration capability of the lamp to yellow and drop off.

Treatment: Make sure to hang your grow lights as per the manufacturer’s instructions. Adjust as plants progress and use a tape measure for precision. These days there are so many new grow light technologies on the market with their own nuances, you really must stick with the manufacturer’s guidelines to position the light in the sweet spot.

Treatment: Make sure to hang your grow lights as per the manufacturer’s instructions. Adjust as plants progress and use a tape measure for precision. These days there are so many new grow light technologies on the market with their own nuances, you really must stick with the manufacturer’s guidelines to position the light in the sweet spot.

FORCES OF NATURE

COLD WEATHER

Temperatures below 10°C will cause the leaves of the majority of cannabis leaves to yellow. Some will even take on purple and bluish tones. Sure, this is a fantastic bonus in the final phase of bloom with some strains, but to be avoided early in the grow.

Treatment: Indoors simply turn up the heat or add more lights to the grow op and turn a negative into a bumper harvest. Outdoor growers might need to take plants inside at nighttime or at least invest in a basic DIY greenhouse.

Treatment: Indoors simply turn up the heat or add more lights to the grow op and turn a negative into a bumper harvest. Outdoor growers might need to take plants inside at nighttime or at least invest in a basic DIY greenhouse.

Treatment: Indoor growers need to turn up the air conditioning and ensure intake and outtake fans are powerful enough for the size of the grow room. Again, we strongly advise consulting the fan manufacturer’s website for performance specifications. Outdoors the best growers can do is construct a simple shade and hope the heatwave is short-lived.

Treatment: Indoor growers need to turn up the air conditioning and ensure intake and outtake fans are powerful enough for the size of the grow room. Again, we strongly advise consulting the fan manufacturer’s website for performance specifications. Outdoors the best growers can do is construct a simple shade and hope the heatwave is short-lived.

PESTS AND PLAGUES

Bugs and nasty microorganisms can easily hitch a ride on your clothes, clones gifted from a pal or on a household pet and invade your grow op. Outdoors quadrupedal furry pests of all shapes and sizes must also be taken into consideration and regarded as hostiles.

Treatment: The cannabis growing area must be sealed off from intruders in so far as practicable indoors or outdoors. Naturally an outdoor grow is impossible to 100% quarantine, so you do what you can. Grow in a quiet sunny spot and use chicken wire to protect plants from nibblers like deer and rabbits.

Treatment: The cannabis growing area must be sealed off from intruders in so far as practicable indoors or outdoors. Naturally an outdoor grow is impossible to 100% quarantine, so you do what you can. Grow in a quiet sunny spot and use chicken wire to protect plants from nibblers like deer and rabbits.

Indoors you have far greater capacity to seal off the grow op. By using a grow tent, restricting entry strictly to you the grower exclusively and keeping basic hygienic practices, you should be able to keep your marijuana lush green and healthy.